US4156711A - Process for the removal of impurities contained in a zinc and cadmium sulfate solution - Google Patents

Process for the removal of impurities contained in a zinc and cadmium sulfate solution Download PDF

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US4156711A
US4156711A US05/850,520 US85052077A US4156711A US 4156711 A US4156711 A US 4156711A US 85052077 A US85052077 A US 85052077A US 4156711 A US4156711 A US 4156711A
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solution
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zinc
acid
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US05/850,520
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Fernand J. J. Bodson
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Societe des Mines et Fonderies de Zinc de la Vieille Montagne SA
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Societe des Mines et Fonderies de Zinc de la Vieille Montagne SA
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    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B7/00Halogens; Halogen acids
    • C01B7/01Chlorine; Hydrogen chloride
    • C01B7/03Preparation from chlorides
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01GCOMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G11/00Compounds of cadmium
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01GCOMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G9/00Compounds of zinc
    • C01G9/06Sulfates
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S204/00Chemistry: electrical and wave energy
    • Y10S204/13Purification and treatment of electroplating baths and plating wastes

Definitions

  • the present invention concerns a process for removing chlorine ions from a zinc sulphate solution or from a cadmium sulphate solution which may contain other impurities, and more particularly a process for removing chlorine, from sulphate solutions for the production of electrolytic zinc or electrolytic cadmium.
  • This method which enables to remove also the various elements Mn, Co, Ni and Tl beside the Cl, has however the drawback that it introduces K ions into the solution; further, the method offers no selectivity at all, all elements being removed at the same time; this is inconvenient especially when one wishes to keep some manganese in the solution in order to protect the lead anodes by means of a MnO 2 precipitate during the electrolysis.
  • the present invention which aims to remove the abovestated drawbacks of the known processes, concerns a process for removing chlorine ions from a sulphate solution of zinc or cadmium which has an acidity of at least 10 g sulphuric acid per liter and which may contain other impurities such as Mn, Tl, Co and Ni, which process comprises adding to said solution the so called acid of Caro or an ammonium or alkali metal salt thereof, whereby the chlorine ions are removed selectively.
  • the acid of Caro that is peroxymonosulphuric acid or H 2 SO 5 is rather unstable.
  • Various processes are known to prepare said acid of Caro or its ammonium or alkali metal salts.
  • the acid of Caro may be obtained by simple hydrolysis of persulphuric acid (H 2 S 2 O 8 ).
  • persulphuric acid H 2 S 2 O 8 is obtained by anodic oxidation of sulphuric acid on platinum anodes using a high current density. This persulphuric acid hydrolyses progressively according to the following reactions:
  • Another method for producing the acid of Caro consists in reacting oleum with hydrogen peroxide at lower temperature; thus, when mixing hydrogen peroxide having a H 2 O 2 content of 70% with oleum containing 25 weight percent of SO 3 , in a molar ratio of total SO 3 :H 2 O 2 comprised between 1.8 and 2, one obtains a final product having the following composition by weight:
  • the produced chlorine is gaseous and may easily be removed by blowing air through the solution.
  • a solution which is free of manganese (IV) salts As an exhausted acid solution of zinc or cadmium leaving an electrolysis cell always contains manganese IV salts, according to another feature of the invention there is added to said solution a conventional art reducing agent, such as an iron (II) salt, preferable iron (II) sulphate, in an amount which is sufficient to discolour the solution; this amount is usually comprised between 100 and 200 mg/l.
  • a conventional art reducing agent such as an iron (II) salt, preferable iron (II) sulphate
  • the chloride content of the treated solution varied with the reaction time as it appears from the following table: the starting solution contained 495 mg chloride per liter;
  • the starting solution contained 495 mg/l chlorine

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)

Abstract

Process for removing chlorine from an acidic zinc or cadmium sulphate solon, comprising adding thereto acid of Caro or an ammonium or alkali metal salt thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. application Ser. No. 693,620, filed June 7, 1976, by Bodson and entitled Process for the Removal of Impurities Contained in a Zinc and Cadmium Solution. This application has matured into U.S. Pat. No. 4,096,233 on June 20, 1978.
SUBJECT-MATTER OF THE INVENTION
The present invention concerns a process for removing chlorine ions from a zinc sulphate solution or from a cadmium sulphate solution which may contain other impurities, and more particularly a process for removing chlorine, from sulphate solutions for the production of electrolytic zinc or electrolytic cadmium.
THE PRIOR ART
At present it is known to remove chlorine by adding a silver salt to the solution; thus a precipitate of silver chloride is obtained which is separated by filtration. This way of proceeding is little economical due to the cost of the silver salt, a part of which is lost during the operations.
This is also known a method which provides adding potassium permanganate to the zinc or cadmium sulphate solution. This method, which enables to remove also the various elements Mn, Co, Ni and Tl beside the Cl, has however the drawback that it introduces K ions into the solution; further, the method offers no selectivity at all, all elements being removed at the same time; this is inconvenient especially when one wishes to keep some manganese in the solution in order to protect the lead anodes by means of a MnO2 precipitate during the electrolysis.
BRIEF DESCRIPTION OF THE INVENTION
The present invention, which aims to remove the abovestated drawbacks of the known processes, concerns a process for removing chlorine ions from a sulphate solution of zinc or cadmium which has an acidity of at least 10 g sulphuric acid per liter and which may contain other impurities such as Mn, Tl, Co and Ni, which process comprises adding to said solution the so called acid of Caro or an ammonium or alkali metal salt thereof, whereby the chlorine ions are removed selectively.
DETAILED DESCRIPTION OF THE INVENTION
The acid of Caro, that is peroxymonosulphuric acid or H2 SO5 is rather unstable. Various processes are known to prepare said acid of Caro or its ammonium or alkali metal salts.
Thus the acid of Caro may be obtained by simple hydrolysis of persulphuric acid (H2 S2 O8).
It is known that persulphuric acid H2 S2 O8 is obtained by anodic oxidation of sulphuric acid on platinum anodes using a high current density. This persulphuric acid hydrolyses progressively according to the following reactions:
H.sub.2 S.sub.2 O.sub.8 +H.sub.2 O→ H.sub.2 SO.sub.5 +H.sub.2 SO.sub.4
h.sub.2 so.sub.5 +h.sub.2 o→ h.sub.2 o.sub.2 +h.sub.2 so.sub.4
therefore it is almost impossible to keep pure persulphuric acid and in general one has a mixture of the three components: H2 S2 O8, H2 SO5 and H2 O2.
In a solution of persulphuric acid, the amounts of each of these three components have been determined after various hydrolysis times at a temperature of 22° C. The results of these analyses are represented in the following Table I.
              TABLE I                                                     
______________________________________                                    
Hydrolysis  H.sub.2 S.sub.2 O.sub.8                                       
                       H.sub.2 SO.sub.5                                   
                                  H.sub.2 O.sub.2                         
time        mole/l     mole/l     mole/l                                  
______________________________________                                    
0           1.45       0.00       0.00                                    
10 min.     1.27       0.18       0.00                                    
30 min.     1.10       0.35       0.00                                    
1 h         0.96       0.51       0.00                                    
 1 h 30     0.81       0.71       0.00                                    
2 h         0.64       0.87       0.010                                   
3 h         0.37       1.07       0.015                                   
5 h         0.15       1.30       0.030                                   
6 h         0.095      1.35       0.040                                   
7 h         0.05       1.37       0.050                                   
10 h        0.015      1.39       0.080                                   
25 h        0.00       1.23       0.20                                    
______________________________________                                    
Another method for producing the acid of Caro consists in reacting oleum with hydrogen peroxide at lower temperature; thus, when mixing hydrogen peroxide having a H2 O2 content of 70% with oleum containing 25 weight percent of SO3, in a molar ratio of total SO3 :H2 O2 comprised between 1.8 and 2, one obtains a final product having the following composition by weight:
H2 so5 :43%; h2 o2 :1%; h2 s2 o8 :1.6%; h2 so4 :44% and H2 O= rest.
It appears that also in this case a mixture of H2 SO5, H2 O2 and H2 S2 O8 is obtained having a maximum H2 SO5 content. When such a mixture of the three components H2 S2 O8, H2 SO5 and H2 O2 is added to a zinc or cadmium sulphate solution containing Cl, this element is oxidized to a removable form.
The following reactions takes place:
ZnCl.sub.2 +H.sub.2 S.sub.2 O.sub.8 →ZnSO.sub.4 +H.sub.2 SO.sub.4 +Cl.sub.2
ZnCl.sub.2 +H.sub.2 SO.sub.5 →ZnSO.sub.4 +H.sub.2 O+Cl.sub.2
The produced chlorine is gaseous and may easily be removed by blowing air through the solution.
It has been found that the chlorine is removed alone or in a selective way, that is to say without other elements, if the reaction is performed in an acid solution, such as for instance a solution issuing from the electrolysis of the zinc or the cadmium; in that case one simply adds the acid of Caro or an ammonium or alkali metal salt thereof to the solution.
In order to favour the removing of the chlorine, there is used according to one feature of the present invention, a solution which is free of manganese (IV) salts. As an exhausted acid solution of zinc or cadmium leaving an electrolysis cell always contains manganese IV salts, according to another feature of the invention there is added to said solution a conventional art reducing agent, such as an iron (II) salt, preferable iron (II) sulphate, in an amount which is sufficient to discolour the solution; this amount is usually comprised between 100 and 200 mg/l.
According to another feature of the invention, there is used acid of Caro which has been obtained by hydrolysing a certain time; tests have shown that a hydrolysis of 10 to 14 hours, at a temperature of 20° C., provides the optimal contents of acid of Caro.
In each of the examples hereafter, when it is mentioned that a stoichiometrical amount of persulphuric acid or acid of Caro solution is used for the oxidation of the element Cl, it is understood that the total amount of the oxidation agents contained in the persulphuric acid or acid of Caro solution, namely H2 S2 O8, H2 SO5 and H2 O2, parttakes to the oxidation reaction of the chlorine ions.
EXAMPLES EXAMPLE 1
Test 1
To an acid solution of zinc sulphate issuing from an electrolysis cell, and containing:
Zn:50 g/l; H2 SO4 :170 g/l; Cl:495 mg/l,
145 mg/l iron (II) sulphate were added in order to reduce the manganese (IV) salts, which is visible to the discolouring of the solution. To the solution heated to 40° C., the stoichiometric amount of freshly prepared persulphuric acid needed for removing the chloride ions, was added at one time, and the formed chlorine was released by blowing air through the solution.
The chloride content of the treated solution varied with the reaction time as it appears from the following table: the starting solution contained 495 mg chloride per liter;
then, after 1 hour: 300 mg/l
then, after 2 hours: 240 mg/l
then, after 3 hours: 210 mg/l
then, after 4 hours: 175 mg/l
then, after 5 hours: 170 mg/l
After 5 hours, the chlorine was removed to an extent of 66%.
Test 2
Using the same solution as in test 1, H2 S2 O8 was added thereto as in said test 1, however without having previously reduced the manganese (IV) salts.
The chloride contents varied with the reaction time in the following way:
The starting solution contained 495 mg/l chlorine;
then, after 1 hour: 375 mg/l
then, after 2 hours: 372 mg/l
then, after 3 hours: 370 mg/l
then, after 4 hours: 364 mg/l
then, after 5 hours: 362 mg/l
In this case one observes that after 5 hours only 27% of the chlorine was removed.
When comparing these two tests of example 1, one clearly sees that the previous reduction of the manganese (IV) salts favours the removing of the chloride ions.
EXAMPLE 2
To an acid zinc sulphate solution, issuing from zinc electrolysis cells, which solution contained:
Zn:52 g/l; H2 SO4 :169 g/l; Cl:700 mg/l
125 mg/l iron (II) sulphate were added in order to reduce the manganese (IV) salts.
To this discoloured solution were added at one time:
in a first test the stoichiometric amount of freshly prepared H2 S2 O8 needed for removing the chlorides;
in a second test, the same amount of H2 S2 O8 which had been hydrolysed during 10 hours;
in a third test, the same amount of H2 S2 O8 which had been hydrolysed during 42 hours at 10° C. The chloride contents were determined after various reaction times of the H2 S2 O8 for each of the three tests. The results are represented in Table 3 below:
              TABLE 3                                                     
______________________________________                                    
                         2          3                                     
               1       H.sub.2 S.sub.2 O.sub.8                            
                                  H.sub.2 S.sub.2 O.sub.8                 
             Freshly   hydrolysed hydrolysed                              
             prepared  during 10 h                                        
                                  during 42 h                             
Test         H.sub.2 S.sub.2 O.sub.8                                      
                       at 12° C.                                   
                                  at 12° C.                        
______________________________________                                    
Chloride con-                                                             
tents at the                                                              
starting     700 mg/l  700 mg/l   700 mg/l                                
after 1 hour 452       295        400                                     
after 2 hours                                                             
             400       238        295                                     
after 3 hours                                                             
             350       212        275                                     
after 4 hours                                                             
             312       175        252                                     
after 5 hours                                                             
             270       165        252                                     
Removement of the                                                         
Cl after 5 hours                                                          
             61.43%    76.43%     64%                                     
______________________________________                                    
From these results, it appears that the removement of the chloride ions is at its maximum when the H2 S2 O8 has been submitted to a duration of hydrolysis corresponding to obtaining the maximum content of acid of Caro.

Claims (5)

I claim:
1. Process for removing chlorine anions from a sulphate solution of zinc or cadmium, having an acidity of at least 10 g sulphuric acid per liter, comprising adding to said solution a solution of H2 SO5 or an ammonium or alkali salt thereof.
2. Process according to claim 1, wherein the solution of H2 SO5 is prepared by hydrolysing a solution of H2 S2 O8 until its H2 SO5 content has reached a maximum.
3. Process according to claim 2, wherein the solution of H2 S2 O8 has been hydrolysed during a time comprised between 10 and 14 hours at a temperature of 20° C.
4. Process according to claim 1, wherein the solution of H2 SO5 is prepared from oleum and hydrogen peroxide.
5. Process according to claim 1, wherein any manganese (IV) salts are reduced to manganese (II) salts by means of iron (II) sulphate, which is added before adding the solution of H2 SO5.
US05/850,520 1975-06-19 1977-11-11 Process for the removal of impurities contained in a zinc and cadmium sulfate solution Expired - Lifetime US4156711A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4198377A (en) * 1977-09-17 1980-04-15 Interox Chemicals Limited Process for recovering manganese from aqueous acidic sulphate solutions
CN104556205A (en) * 2014-12-31 2015-04-29 袁福堂 Technical method for producing feed-grade zinc sulfate in environment-friendly manner by electrolytic zinc slag

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US570624A (en) * 1896-11-03 William donald
US1066245A (en) * 1912-12-09 1913-07-01 Anson G Betts Production of zinc sulfate.
US1310943A (en) * 1919-07-22 Rasiklai datta
US1444484A (en) * 1919-09-25 1923-02-06 Little Inc A Metallurgical process for treatment of zinc compounds
GB370965A (en) * 1929-11-25 1932-04-08 Nichols Copper Co Improvements in or relating to processes for eliminating chlorine from solutions containing zinc chloride and to improved solutions obtained thereby
US1879577A (en) * 1929-07-12 1932-09-27 Ig Farbenindustrie Ag Process for precipitating iron from the solutions freed from copper obtained by burning pyrites with chlorine
US2145816A (en) * 1937-04-20 1939-01-31 Hercules Powder Co Ltd Purification of zinc salt solutions
US2746840A (en) * 1952-07-24 1956-05-22 Dow Chemical Co Purification of concentrated salt solutions
US2977221A (en) * 1958-11-17 1961-03-28 Little Inc A Nickel-cobalt separation
US3215627A (en) * 1962-11-26 1965-11-02 Alto Chemical Lab Inc Pool sterilization
US3393046A (en) * 1966-02-21 1968-07-16 Giganov Georgy Petrovich Method for purification of zinc sulphate solutions
GB1371302A (en) * 1973-05-11 1974-10-23 Shell Int Research Removal of chloride from crude zinc sulphate solutions
SU496237A1 (en) * 1974-04-18 1975-12-25 Московский Ордена Ленина И Ордена Трудового Красного Знамени Химикотехнологический Институт Им. Д.И.Менделеева The method of purification of zinc sulphate solutions from chlorine
US4005174A (en) * 1974-06-17 1977-01-25 Fernand Jacques Joseph Bodson Process for the elimination of chloride from zinc sulphate solutions

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US570624A (en) * 1896-11-03 William donald
US1310943A (en) * 1919-07-22 Rasiklai datta
US1066245A (en) * 1912-12-09 1913-07-01 Anson G Betts Production of zinc sulfate.
US1444484A (en) * 1919-09-25 1923-02-06 Little Inc A Metallurgical process for treatment of zinc compounds
US1879577A (en) * 1929-07-12 1932-09-27 Ig Farbenindustrie Ag Process for precipitating iron from the solutions freed from copper obtained by burning pyrites with chlorine
GB370965A (en) * 1929-11-25 1932-04-08 Nichols Copper Co Improvements in or relating to processes for eliminating chlorine from solutions containing zinc chloride and to improved solutions obtained thereby
US2145816A (en) * 1937-04-20 1939-01-31 Hercules Powder Co Ltd Purification of zinc salt solutions
US2746840A (en) * 1952-07-24 1956-05-22 Dow Chemical Co Purification of concentrated salt solutions
US2977221A (en) * 1958-11-17 1961-03-28 Little Inc A Nickel-cobalt separation
US3215627A (en) * 1962-11-26 1965-11-02 Alto Chemical Lab Inc Pool sterilization
US3393046A (en) * 1966-02-21 1968-07-16 Giganov Georgy Petrovich Method for purification of zinc sulphate solutions
GB1371302A (en) * 1973-05-11 1974-10-23 Shell Int Research Removal of chloride from crude zinc sulphate solutions
SU496237A1 (en) * 1974-04-18 1975-12-25 Московский Ордена Ленина И Ордена Трудового Красного Знамени Химикотехнологический Институт Им. Д.И.Менделеева The method of purification of zinc sulphate solutions from chlorine
US4005174A (en) * 1974-06-17 1977-01-25 Fernand Jacques Joseph Bodson Process for the elimination of chloride from zinc sulphate solutions

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4198377A (en) * 1977-09-17 1980-04-15 Interox Chemicals Limited Process for recovering manganese from aqueous acidic sulphate solutions
CN104556205A (en) * 2014-12-31 2015-04-29 袁福堂 Technical method for producing feed-grade zinc sulfate in environment-friendly manner by electrolytic zinc slag

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